The invention is generally directed to toner and developer compositions, and more specifically, the present invention is directed to developer and toner compositions containing charge enhancing additives, which impart or assist in imparting a negative charge to the toner particles and enable toners with rapid triboelectric charging characteristics. In one embodiment, there are provided in accordance with the present invention toner compositions comprised of a polymer or polymer resins, pigment particles or dye molecules, and certain aryl sulfone charge enhancing additives. In another embodiment, the present invention is directed to toners with hydroxyaryl sulfones, particularly unsymmetrical hydroxyaryl sulfone charge enhancing additives, which additives can be obtained from the reaction of a phenol with one molar equivalent of sulfuric acid, followed by condensation of the resulting hydroxyaryl sulfonic acid with another phenol. In a further embodiment, the present invention relates to the provision of toners with bis(dihydroxyaryl) sulfone charge enhancing additives, which additives are synthesized from the condensation of sulfuric acid with two molar equivalents of a hydroxyphenol. The aforementioned charge additives in embodiments of the present invention enable, for example, toners with rapid triboelectric charging characteristics, extended developer life, stable triboelectrical properties irrespective of changes in environmental conditions, and high image print quality with substantially no background deposits. Also, the aforementioned toner compositions usually contain a colorant or colorants comprised of, for example, carbon black, magnetites, or mixtures thereof, color pigments or dyes of cyan, magenta, yellow, blue, green, red, or brown color, or mixtures thereof thereby providing for the development and generation of black and/or colored images. The toner and developer compositions of the present invention can be selected for electrophotographic, especially xerographic, imaging and printing processes, including color processes.
Toners with negative charge additives are known, reference for example U.S. Pat. Nos. 4,411,974 and 4,206,064, the disclosures of which are totally incorporated herein by reference. The '974 patent discloses negatively charged toner compositions comprised of resins, pigment particles, and as a charge enhancing additive ortho-halophenyl carboxylic acids. Similarly, there are disclosed in the '064 patent toner compositions with chromium, cobalt, and nickel complexes of salicylic acid as negative charge enhancing additives. In U.S. Pat. No. 4,845,003 there are illustrated negatively charged toners with certain aluminum salt charge additives. More specifically, this patent discloses as charge additives aluminum complexes comprised of two or three hydroxybenzoic acid ligands bonded to a central aluminum ion. While these charge additives may have the capability of imparting negative triboelectric charge to toner particles, they are generally not as efficient as desired in promoting the rate of triboelectric charging of the toner particles. A fast rate of triboelectric charging is particularly crucial for high speed xerographic machines since, for example, these machines consume toner rapidly, and fresh toner has to be constantly added. The added uncharged toners therefore must charge up to their equilibrium triboelectric charge level rapidly to ensure no interruption in the xerographic imaging or printing operation. Another shortcoming of these charge additives is their thermal instability, that is they often break down during the thermal extrusion process of the toner manufacturing cycle. Additionally, the hydroxybenzoic acid ligands, particularly 3,5-di-tert-butylsalicylic acid, are expensive precursors for these additives. Furthermore, many of these charge additives contain metals, and when utilized in higher concentrations, they may not meet environmental safety legislation requirements. Most or many of these and other disadvantages are eliminated, or substantially eliminated with the metal complex charge additives of the present invention.
Developer compositions with charge enhancing additives, which impart a positive charge to the toner particles, are also well known. Thus, for example, there is described in U.S. Pat. No. 3,893,935 the use of quaternary ammonium salts as charge control agents for electrostatic toner compositions; U.S. Pat. No. 4,221,856 which discloses electrophotographic toners containing resin compatible quaternary ammonium compounds in which at least two R radicals are hydrocarbons having from 8 to about 22 carbon atoms, and each other R is a hydrogen or hydrocarbon radical with from 1 to about 8 carbon atoms, and A is an anion, for example, sulfate, sulfonate, nitrate, borate, chlorate, and the halogens such as iodide, chloride and bromide, reference the Abstract of the Disclosure, and column 3; a similar teaching is presented in U.S. Pat. No. 4,312,933 which is a division of U.S. Pat. No. 4,291,111; similar teachings are presented in U.S. Pat. No. 4,291,112 wherein A is an anion including, for example, sulfate, sulfonate, nitrate, borate, chlorate, and the halogens; U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, illustrates developer compositions containing as charge enhancing additives organic sulfate and sulfonates, which additives can impart a positive charge to the toner composition; U.S. Pat. No. 4,298,672, the disclosure of which is totally incorporated herein by reference, illustrates positively charged toner compositions with resins and pigment particles, and as charge enhancing additives alkyl pyridinium compounds.
Although many charge enhancing additives are known, there continues to be a need for charge enhancing additives which when incorporated in toners, provide many of the advantages illustrated herein. There is also a need for negative charge enhancing additives which are useful for incorporation into black and colored toner compositions which can be utilized for developing positive electrostatic latent images. Moreover, there is a need for toner compositions utilizing charge enhancing additives which do not contain heavy metals. Furthermore, there is a need for colored toner compositions containing substantially nontoxic charge enhancing additives which do not interfere with the color quality of the colorants present in the toners. Another need relates to the provision of toner compositions with certain charge enhancing additives, which toners in embodiments thereof possess substantially stable triboelectric charge levels, and display acceptable rates of triboelectric charging characteristics. Furthermore, there is also a need for toner compositions with certain charge enhancing additives which possess excellent dispersibility characteristics in toner resins, and can therefore form stable dispersions in the toner compositions. There is also a need for negatively charged black and colored toner compositions that are useful for incorporation into various imaging processes, inclusive of color xerography, as illustrated in U.S. Pat. No. 4,078,929, the disclosure of which is totally incorporated herein by reference; laser printers; and additionally a need for toner compositions useful in imaging apparatuses having incorporated therein layered photoresponsive imaging members, such as the members illustrated in U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference. Also, there is a need for negative toner compositions which have desirable triboelectric charge levels of preferably from between about -10 to about -40 microcoulombs per gram, and triboelectric charging rates of less than about 5 minutes, and preferably less than 2 minutes as measured by standard charge spectrograph methods when the toners are frictionally charged against suitable carrier particles via conventional roll milling techniques. There is also a need for nontoxic, substantially nontoxic, or environmentally compatible charge enhancing additives which when incorporated at effective concentrations of, for example, less than 10 weight percent, preferably less than 5 weight percent in toners, render such toners environmentally acceptable. An additional need resides in the provision of simple and cost-effective preparative processes for the preparation of sulfone charge enhancing additives. The concentrations of the charge additives that can be incorporated into the toner compositions generally ranges from about 0.05 weight percent to about 5 weight percent, depending on whether the charge additive is utilized as a surface additive or as a dispersion in the bulk of the toner. The effective concentrations of toner in the developer, that is toner and carrier particles, are for example from about 0.5 to about 5 weight percent, and preferably from about 1 to about 3 weight percent.
Illustrated in copending patent applications U.S. Ser. No. 894,688 (and U.S. Ser. No. 894,690 ( are toner compositions with metal charge enhancing additives, and more specifically, a negatively charged toner composition comprised of a polymer or polymer resins, a colorant or colorants, optional surface additives, and a metal complex charge enhancing additive obtained from the reaction of a hydroxybenzoic acid and a base with a mixture of a metal ion and a hydroxyphenol; and a negatively charged toner composition comprised of a polymer or polymers, a colorant or colorants, optional surface additives, and a metal complex charge enhancing additive obtained from the reaction of a hydroxybenzoic acid and a base with a mixture of a metal ion and an aromatic dicarboxylic acid.